ABSTRACT
Leucine kinetics were studied in six obese subjects (W/H2 = 39 +/- 4) and six normal subjects (W/H2 = 21 +/- 3) before and after an oral load of 150 g glucose. An intravenous infusion of 1(-13)C leucine was given to the fasting subjects for 450 min: a steady state of plasma leucine enrichment was established 90 min after the start of the infusion, and the glucose load was given 220 min after the start of the infusion. Compared with the lean controls the obese subjects showed a greater area under the curve of blood glucose after the glucose load (P less than 0.025) and higher insulin and glucagon levels both before and after the meal (P less than 0.05), thus indicating the well-known insulin insensitivity of obese (but not diabetic) subjects with respect to glucose metabolism. After the glucose load the lean subjects showed a significant and sustained decrease in leucine oxidation (from 20.0 +/- 2.2 to 13.3 +/- 1.5 mumol/kg LBM/h: P less than 0.01). This response is similar to that observed when insulin-dependent diabetic subjects are given insulin. However the obese subjects showed no decrease in leucine oxidation after the glucose meal (20.3 +/- 1.9 before, and 21.2 +/- 3.6 after). This indicates that obese subjects show insensitivity to the action of insulin with respect to protein metabolism as well as carbohydrate metabolism.
Subject(s)
Glucose/administration & dosage , Leucine/metabolism , Obesity/metabolism , Administration, Oral , Adult , Blood Glucose/analysis , Female , Glucagon/blood , Humans , Insulin/blood , Leucine/administration & dosage , Male , Middle AgedABSTRACT
It is claimed that commercial preparations of an alpha-amylase inhibitor, taken in tablet form 10 min before a meal, will inhibit the digestion of up to 100 g starch in the following meal. This was tested by giving five obese women three meals each containing cornflour enriched with 13C after a tablet of 'Starchex' or 'Calorex' or a placebo, in randomized sequence. The response to the meal in the rate of evolution of 13CO2, the increase in plasma insulin and the increase in blood sugar did not differ with the type of tablet which preceded the meal. We conclude that these starch-blocker tablets do not affect starch digestion or absorption in vivo.